EP0250660A1 - Procédé et dispositif de mesure de la vitesse d'un fluide - Google Patents

Procédé et dispositif de mesure de la vitesse d'un fluide Download PDF

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Publication number
EP0250660A1
EP0250660A1 EP86304280A EP86304280A EP0250660A1 EP 0250660 A1 EP0250660 A1 EP 0250660A1 EP 86304280 A EP86304280 A EP 86304280A EP 86304280 A EP86304280 A EP 86304280A EP 0250660 A1 EP0250660 A1 EP 0250660A1
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Prior art keywords
station
acoustic waves
signals
frequency
signal
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EP86304280A
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German (de)
English (en)
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EP0250660B1 (fr
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James O. Moore
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Moore Products Co
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Moore Products Co
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Priority to US06/723,501 priority Critical patent/US4616510A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters

Definitions

  • This invention relates to a method and apparatus for the measurement of the velocity of fluids, and par­ticularly to such method and apparatus which utilize the transmission of acoustic waves through the moving fluid.
  • each such transducer serv­ing alternatively as a transmitter and a receiver of acous­tic waves. More particularly, first one transducer acts as a transmitter to transmit acoustic waves to the other transducer acting as a receiver, and then the other trans­ducer is caused to transmit acoustic waves to the first transducer which then acts as a receiver. In this way, undesired differences in upstream and downstream acoustic wave delays due to use of different transducers for the two directions of transmission are greatly mitigated.
  • acoustic fluid velocity measuring systems include the Doppler frequency system which detects apparent changes in acoustic wave frequency due to fluid motion, but which has the drawback that particles must normally be present in the fluid in order to develop a suitable signal, and that accuracy is usually limited to about 5% at best.
  • a limi­tation of this method is that in order to get the nec­essary resolution of the pulses, the transducer must op­erate in the megahertz region where propagation losses are undesirably high in liquids, and so high in gases as to make the system virtually unuseable. Also, the necessity for transmitting and receiving a narrow pulse limits the energy available for detection, and for best results requires use of transducers with very wide band­widths.
  • Phase comparison methods are also known to mea­sure the fluid velocity.
  • the phase of the transmitted signal is compared to that of the received signal; typically the phase delay for downstream propaga­tion is compared with the phase delay for upstream pro­pagation to give a sensitive measurement of fluid flow rate.
  • This technique has the advantage that greater sig­nal power can be transmitted than when only a narrow trans­mitted pulse is used, providing a better signal to noise ratio.
  • the frequencies employed are lower than in the narrow-pulse system, making operation in gas prac­tical, with generally less attenuation in any medium.
  • phase comparison methods depend on knowledge of ambient sound velocity v0, which varies widely with temperature and type of fluid. Also, accuracy will generally suffer if there are any significant re­flections of the acoustic waves from the transducers or from the surrounding walls of the fluid chamber. Par­ticularly troublesome are triple reflections directly off the transducer faces themselves. Standing waves caused by such reflections can often affect the accuracy by 50% or more; also, linearity as the function of fluid velocity is affected by such standing waves.
  • Another object is to provide such method and apparatus which retain the principal advantages of the phase comparison methods of measurement previously known, but avoid or greatly reduce the drawbacks associated with previously known phase comparison methods.
  • Still another object is to provide such method and apparatus which is accurate over a wide range of tem­peratures and fluid types and compositions, and at the same time provides accurate measurement.
  • the velocity of the fluid is determined by transmitting through it at different times acoustic waves of different frequen­cies, rather than of the same frequencies, and detecting the differences in phase delay of such transmitted signals due to the differences in frequencies between the acoustic waves producing the phase delays.
  • the signals representing the differences in the frequencies and the corresponding differences in the phase delays of the acoustic waves are used to determine the velocity of the fluid through which the waves propagate.
  • the fluid velocity V f may be expressed as: where L is the spacing between a pair of transmitting and receiving acoustic transducers, ⁇ d is the change in phase delay of the downstream acoustic wave due to a shift ⁇ f d in frequency, and ⁇ u is the change in phase delay of the acoustic waves transmitted upstream due to a shift in frequency ⁇ f u .
  • ⁇ d / ⁇ f d and ⁇ u / ⁇ f u may be represented as the slopes M d and M u , of straight line graphs representing the relationship between frequency and phase delay for the downstream and upstream transmission cases respectively.
  • the measurement described above utilizing a pair of different transmission frequencies in each direction of propagation provides an indication of each of these slopes.
  • spurious signals caused by such things as undesired re­flections and second-round echoes from the transducers in practice these graphs for the up and down transmissions are not the idealized straight lines one might expect.
  • the pairs of frequencies utilized to determine the frequency versus phase-delay slopes are preferably close enough to each other that the correspond­ing differences in phase delay are less than 360° (2 ⁇ radians). In such cases there is never any ambiguity in the measurement with respect to whether the phase delay that occurs is equal to the measured value ⁇ or to a phase delay ⁇ + N2 ⁇ , as would otherwise occur when utilizing a conventional phase comparison type of phase detector.
  • the frequency differences used can be constant, can be the same for upstream and downstream measurements, can be equal or unequal to each other, or can be random with respect to frequency and with respect to frequency dif­ference.
  • phase change produced by a diff­erence ⁇ f in frequency of a pair of transmitted frequencies may be less than 360°, but may bridge the zero-phase condition of the phase comparator; for example, f1 might produce a phase delay ⁇ 1 of 350° and f2 might produce a phase delay ⁇ 2 of 370°, giving a phase difference ⁇ 2- ⁇ 1 of 20°. Since the typical phase detector would sense a change from 350° to 10°, rather than from 350° to 370°, its output would typically provide a false indication of ⁇ 2- ⁇ 1.
  • ap­paratus which detects such an anomalous direction of change between frequencies of a frequency pair, and to add 360°, or 2 ⁇ radians, to the second measurement, so that the measured difference between the phase delays due to the two different frequencies will be correct.
  • a novel technique is used in which the frequencies of all received transmissions are divided by a factor D such that even though the phases of the received signals may extend over several multiples of 360°, the frequency-divided signal exhibit phase changes of less than 360°, and the phase ambiguity is thereby removed.
  • FIG. 1 there is shown a conduit 10 through which a fluid flows in the direction of the arrows.
  • a pair of transmitter-receiver acoustic transducers 12 and 14 face each other across the conduit, along a line 16 extending obliquely across the conduit, so that the fluid flow has a component along the direction of the conduit axis A-A1.
  • Each transducer is chosen to be able to transmit acoustic waves at appropriate fre­quencies through the fluid to the other transducer, and each is also capable of acting as an efficient receiver of such waves from the other transducer.
  • one transducer may be used first as a transmitter while the other one is used as a receiver, and then the other may be used as a transmitter while the first one acts as a receiver.
  • the ultimate objective is to measure the velocity of fluid flow along the axis of the con­duit, which is done by measuring the velocity V F along the axis 16 of the transducers and multiplying this by a known constant equal to the cosine of the angle ⁇ be­tween the tranducer axis and the conduit axis.
  • Reversing switch 22 is shown schematically as a mechanical double-poled double-throw switch, with cross-connections to achieve reversal, but it will be understood that in actuality it will almost always be a high-speed electronic switch performing these same func­tions.
  • the reference electrical oscillations from oscillator 20 are supplied by the switch 22 to transducer 12 for transmission, and are received by transducer 14; in the opposite position of the switch shown in broken line, the oscillations are supplied to the other transducer 14 for transmission and are received by transducer 12.
  • Received signals from the transducers are sup­plied over line 23 to a phase detector 24, by way of an amplifier and tracking filter 25, a pulse shaper 26 and a frequency divider 27 which is part of the receiver for the system.
  • Amplifier and tracking filter 25 may be con­ventional, and is supplied with a tracking control signal from oscillator 20 over line 28 so that the passband of the filter will automatically track the frequency of the received signal and thus enable efficient noise rejection.
  • Shaper 26 may also be conventional, and serves to convert the amplified received signals into corresponding square wave signals.
  • the frequency divider 27 has a special pur­pose, described in detail hereinafter.
  • the phase detector 24 is also supplied with the original frequency-controlled oscillations from os­cillator 20 over line 28 by way of a conventional shaper 29 and a special divider 50, the latter signal serving as a reference phase signal for the phase detector.
  • the phase detector 24 produces an output on its output line 32 which is indicative of the phase delay ⁇ of the signal received by the phase detector, relative to the phase of the signal at the oscillator and at the transmitting tranducer.
  • the phase-delay indicating signal on output line 32 is supplied to a low-pass filter 34 and then through an LSA apparatus 36 to a velocity computation apparatus 38, which produces an output signal representa­tive of the velocity V F of the fluid in conduit 10 along the line 16 in Figure 1.
  • the oscillator 20 is controlled by the counter and logic apparatus 40 and by a clock oscillator 42, to generate and supply to the transducers oscillations at predetermined controlled frequencies, which may be de­signated f1, f2...f n .
  • Counter and logic apparatus 40 also produces a signal f s which acts over line 44 to operate the switch 22, as well as other timing signals described hereinafter.
  • the apparatus of Figure 1 will measure the upstream phase delay ⁇ u for each of a plurality of frequencies and thus develop a set of signals ( ⁇ ui , f ui ) representing corresponding pairs of values of phase delay and frequency; similarly, the equipment measures the down­stream phase delay ⁇ d for each of the same plurality of frequencies to produce corresponding pairs of frequency and delay data ( ⁇ di , f di ).
  • the data ( ⁇ ui , f ui ) and ( ⁇ di , f di ) are then used to compute the desired fluid velocity V f from the latter input information and from a knowledge of the transducer separation L.
  • V F fluid velocity along direction of acoustic waves.
  • v u acoustic wave velocity upstream
  • v d acoustic wave velocity downstream
  • L distance between upstream and downstream stations
  • v0 velocity of acoustic waves at zero flow velocity.
  • v u v0 - V F
  • v d L/t d
  • v u L/t u , (2) where t d and t u are wave transit times down and up stream.
  • the incremental slope equals the overall slope ⁇ /f, and that can be measured readily, accurately, and without phase ambiguity. Accordingly, pursuant to the invention one may evaluate equation (7) by measuring ⁇ u , ⁇ f u , ⁇ d and ⁇ f d , and computing V F , preferably by the formula:
  • Figs. 2A and 2B abscissae represent transmitted frequencies and ordinates represent phase delay of signals propagating between the two transducers by way of the moving fluid, while in Fig. 2B ordinates represent phase delay and abscissae represents the output voltage E ⁇ of the phase detector.
  • Fig. 2A abscissae represent transmitted frequencies and ordinates represent phase delay of signals propagating between the two transducers by way of the moving fluid
  • Fig. 2B ordinates represent phase delay
  • abscissae represents the output voltage E ⁇ of the phase detector.
  • the difference between the frequency f1 and the frequency f2 is designated as ⁇ f1
  • the difference between frequency f2 and f3 is designated ⁇ f2 and so on.
  • the frequency differences utilized are f2-f1, f3-f2, f4-f3, f5-f4, and f6-f5.
  • Each of these frequencies f1 through f6 pro­duces a signal having a corresponding phase delay in trans­it through the fluid; for f1 the delay is ⁇ d1 , for f2 it is ⁇ d2 , etc. during downstream transmission, while for upstream transmission f1 produces the phase delay ⁇ u1 , f2 produces the phase delay ⁇ u2 , etc.
  • These dif­ferences in phase delay corresponding to ⁇ f1, ⁇ f2, etc. are ⁇ d2 - ⁇ d1 and ⁇ d3 - ⁇ d2 etc. for the downstream trans­mission, and ⁇ u2 - ⁇ u1 and ⁇ u3 - ⁇ u2 etc. for the upstream transmission.
  • the phase delay difference ⁇ d2 - ⁇ d1 is designated herein as ⁇ d1 corresponding to the frequency difference ⁇ f1, and similarly for the other frequency and phase delay increments.
  • the straight-line graph in Fig. 2A designated "Downstream” is the idealized straight-line graph, of slope M d , defining the idealized proportionality constant between frequency and phase delay for the downstream transmission case, for an arbitrary fluid velocity. For other velocities, its slope will be different.
  • the portions of that graph between the plotted data points for the six different fre­quencies have incremental slopes indicated as M d1 , M d2 , etc., and in this idealized case each of these incremental slopes is the same as the overall slope M d .
  • the upper straight-line graph designated "Up­stream” is the corresponding graph defining the idealized relationship between frequency and phase delay for up­stream transmissions, and the overall slope thereof may be designated as M u , with its incremental slopes indicated as M u1 , M u2 , etc.
  • FIG. 2B Shown in Figure 2B, at the right-hand side, is a graph showing the idealized output voltage E ⁇ of a standard phase detector used in the position of phase detector 24 of Figure 1, as it would be produced by the various phase delays ⁇ of Fig. 2A due to the various fre­quencies f.
  • the dots on the straight-line graph of E ⁇ represent the phase detector output voltages for the upstream and downstream transmissions at f1 through f6. These coordinate represent the ( ⁇ ui , f ui ) and ( ⁇ ui , f di ) data referred to above.
  • Figure 3 illustrates the general timing arrange­ment utilized in this preferred form of the invention.
  • the signal transmitted by one of the transducers say transducer 12, first at a frequency f u , and then at a frequency f u2 ; while during actual transmission through the fluid the signals may not have the idealized rectangular shape shown, they ap­proach this form after reception and shaping, and since the timing considerations are the same, for simplicity the signal is shown as comprising rectangular pulses throughout the waveform diagrams.
  • the output of divider 50, shown at B is the same as the output of divider 27, shown at D, except that the entire waveform D is delayed by ⁇ .
  • the phase detector 24 receives the signals B and D from the dividers, and produces an output therefrom shown at E which has a duty cycle proportional to the phase differences between sig­nals B and D. That is, the percentage of the time for which the output of the phase detector is high is pro­portional to ⁇ and inversely proportional to the wave period P.
  • This percentage of time, equal to ⁇ /P, there­fore represents the phase delay of the acoustic wave, and is detected by filter 34.
  • f increases (as from f u1 to f u2 ), and the corresponding period P of the acoustic waves decreases, the output of phase detector 24 increases toward 100%.
  • the effective period P is increased for measurement purposes by the divider fact­or D, and the delay ⁇ can therefore vary over about a D times greater range, without ambiguity of output, than if the described divider system were not used.
  • the trans­mitted frequencies are exactly known by the equipment which generates them, and it is therefore only the cor­responding values of phase delay ⁇ which need to be mea­sured and which therefore are subject to some error.
  • the transmitted frequencies are varied in equal steps.
  • a graph of ⁇ as a function of transmitted frequency should ideally be a straight-­line of slope M, but, as mentioned previously, due to errors the measured values of ⁇ will be scattered on each side of the ideal straight line.
  • a least-squares algorithm is preferably used in this example to arrive at the actual value of M to be used in the formula for computing fluid velocity V F . It will be understood that there are many other ways that the value of M could be arrived at, in­cluding various known averaging and curve-fitting techniques. However, the LSA approach is believed to produce a worth­while improvement in results compared with such other methods.
  • M ⁇ 7 ⁇ 1 + 5 ⁇ 2 + 3 ⁇ 3 + ⁇ 4 - ⁇ 5 - 3 ⁇ 6 - 5 ⁇ 7 - 7 ⁇ 8 (13)
  • the latter algorithm is implemented by the LSA apparatus 36, comprising in this example a non-inverting amplifier 70 connected to a time-weighting switch 72 by way of a gating switch 74, and a reversing amplifier 78 connected to the time-­weighting switch 72 by way of a gating switch 80.
  • the output of switch 72 represents, at successive times, the successive terms in the expression for M ⁇ in equation (13). Positive terms are produced by turning on switch 74 but not switch 80 and negative times by turning on switch 80 but not switch 74.
  • the successive values of a i i.e. 7, 5, 3, 1, -1, -3, -5, -7) are produced by turning on time-weighting switch 72 for periods of time proportional to the corresponding coefficient.
  • the output M ⁇ of the LSA apparatus 36 is supplied in parallel to switches 82 and 84.
  • switch 82 When transmissions through the fluid in the upstream direction are being received, switch 82 is closed to pass the LSA output, while switch 84 is open, and conversely when downstream transmissions are being received.
  • the output of switch 82 therefore represents the successive terms in the algo­rithm representing M ⁇ for upstream transmission, and the output of switch 84 represents the corresponding terms for the downstream transmission.
  • the output of switch 82 is supplied to an in­tegrator 86 which sums the term-representing signals sup­plied to it between successive resets, i.e. forms such a sum for each frequency sweep during upstream transmission; an integrator 88 is supplied with the output of switch 84 at alternate times, to sum up the term-representing signals for each frequency sweep during downstream trans­missions. Accordingly, the output of integrator 86 re­presents M ⁇ u and the output of integrator 88 represents M ⁇ D . Each of these integrators may be a known commercially-­available device. Reset pulses are applied to each inte­grator over reset lines 90 and 92, at the end of each frequency sweep.
  • the outputs of the two integrators are supplied to respective sample-and-hold devices 94 and 96, which are actuated at times controlled by pulse signal f s to sample the outputs of each integrator after each frequency sweep of the signals supplied to it, and to hold these sampled values until the next pulse f s .
  • the outputs of the sample-and-hold devices are supplied to respective analog multipliers 97 and 98 connected in the feedback paths of respective operational amplifiers 99 and 100.
  • Each of these com­binations will act as a func­tional inverter, i.e. will produce at the output terminal of the amplifier a signal which varies as the inverse function, or reciprocal, of the input signal. Accordingly, the output of amplifiers 99 and 100 are proportional to the functions 1/M ⁇ u and 1/M ⁇ D respectively.
  • the signal level applied to the + input terminals of the operational amplifiers from level source 101 acts as a multiplicative scaling factor for the output signals, and in this case such level is preferably adjusted to produce a scaling factor equal to ; accordingly, the two amplifiers out­puts represent, respectively, the functions ⁇ L/M u and ⁇ L/M D .
  • a low-pass filter 120 may optionally be used to smooth the output signal, and if used preferably has a breakpoint frequency some­what lower then the upstream-downstream switching rate.
  • the level applied to the amplifiers 99 and 100 from source 101 may also include a scaling factor cosine ⁇ , if it is desired that the output signal directly repre­sent fluid velocity along the conduit axis A-A ⁇ , rather than the velocity V F along the transducer axes.
  • E ⁇ ⁇ mod 2 ⁇ . (14) That is, E ⁇ is a monotonically increasing function f phase delay ⁇ ; e.g. ⁇ increases from zero to 2 ⁇ radians, and repeats this every 2 ⁇ radians. This gives a sawtooth characteristic, such as is shown for E ⁇ in the graph of Figure 2B.
  • ⁇ ⁇ c , where ⁇ is the time delay of the a­coustic waves in travelling from one acoustic transducer to the other and ⁇ c is the acoustic wave frequency in radians per second.
  • ⁇ max ⁇ 2 ⁇ .
  • the dividing factor D may be selected so that the following is true: D > ⁇ f max , (16) where f max is the highest acoustic-wave frequency used in the measuring process. With such a value for D, the phase delay never exceeds the period P of the acoustic wave cycle and phase ambiguity is therefore avoided.
  • the received signal is always present, i.e. the switching between frequencies in each frequency sweep is substantially instantaneous.
  • the frequency of reference oscillator 20 in Figure 1 is incremented by clock oscillator 42 so that, in the example of Figure 3, the f8 signal transmission starts at clock pulse 8 and persists after clock pulse 9 until clock pulse 10, at which time the frequency is shifted to f1.
  • Phase ambiguity is then avoided by selecting D to meet the following condition: D > ( ⁇ + 1/f8) ⁇ F, where ⁇ F is the total fre­quency sweep, e.g. from f1 to f8.
  • the distance between transducers may be about 0.216 meter; the velocity of sound in air under normal operating conditions is about 330 meters/second.
  • the pro­pogation time delay ⁇ is shown as amounting to only a cycle or so of the transmitted frequency.
  • the transit delay ⁇ is ac­tually equal to a time of from about 20 to 28 cycles of the acoustic wave.
  • the phase-delay values ⁇ are not valid, since during such time (about 0.65 ms in this example) the reference signal will represent the trans­mitted signal at the new frequency while the received signal will still be that due to the previous transmission at the former frequency.
  • the weighting pulses f w are preferably not applied to render conductive the time-weighting switch 72 in Figure 5 until at least .65 ms after each frequency shift. Also, because of the slow response of the filter 34, the weighting pulses should typically be delayed 2 to 3 ms after each change of fre­quency anyway. Figure 3, for clarity, does not show such a gap between successive weighting pulses, but for the above reasons a minimum gap of about 2 ms between them is preferably provided.
  • the maximum weighting pulse is chosen at about 3 ms, with a gap time of about 2 ms, a total of about 5 ms could be required for each frequency trans mission. This would theoretically permit use of as many as about 500 phase samples per frequency sweep if desired, rather than the eight used in the present example, while allowing for one "upstream” sweep and one "downstream” sweep per half-second, to give a complete output-informa­tion update once each second, if so desired.
  • FIG. 4 With regard to the overall timing of the exempli­fied system, reference is made especially to the timing diagrams of Fig. 4.
  • Counter and control logic 40 is supplied with these clock pulses and at each clock pulse increments by one frequency step the frequency of signal supplied to the transducer emitting at that time.
  • eight frequencies per sweep are used, the first frequency f1 starting at clock pulse 1 and continuing until clock pulse 2, at which time the frequency is switch­ed to the next frequency f2, and so on until the eighth frequency terminates at clock pulse 9, shortly after which the reset pulse of Fig. 4C occurs.
  • the f s pulse of Fig. 4B begins at clock pulse 1, and has width such that its trailing edge defines the desired time for occurrence of the reset pulse.
  • the weighting pulse signal f ⁇ applied to switch 72 in Fig. 5 corresponds to the values of the coefficients a i used in the LSA procedure; as mentioned above, a small gap will preferably be provided between all weighting pulses, including the ⁇ 1 and ⁇ 2 pulses.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)
EP86304280A 1985-04-15 1986-06-05 Procédé et dispositif de mesure de la vitesse d'un fluide Expired - Lifetime EP0250660B1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US06/723,501 US4616510A (en) 1985-04-15 1985-04-15 Fluid velocity measuring method and apparatus
EP86304280A EP0250660B1 (fr) 1986-06-05 1986-06-05 Procédé et dispositif de mesure de la vitesse d'un fluide

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EP86304280A EP0250660B1 (fr) 1986-06-05 1986-06-05 Procédé et dispositif de mesure de la vitesse d'un fluide

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EP0250660B1 EP0250660B1 (fr) 1991-03-27

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992017753A1 (fr) * 1991-03-26 1992-10-15 Endress + Hauser Limited Debitmetre acoustique
US5714321A (en) * 1986-11-24 1998-02-03 Gen-Probe Incorporated Nucleic acid probes and methods for detecting salmonella
WO2018095562A1 (fr) * 2016-11-24 2018-05-31 Diehl Metering Gmbh Procédé de mesure de temps du propagation d'un signal ultrasonore dans un fluide en écoulement

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2921467A (en) * 1957-08-21 1960-01-19 Albert L Hedrich Flowmeter compensation for propagation velocity changes
EP0007782A1 (fr) * 1978-07-22 1980-02-06 Robert James Redding Dispositif de mesure de l'écoulement d'un fluide

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3671516D1 (de) * 1985-09-30 1990-06-28 Siemens Ag Verfahren zur messung von stroemungsgeschwindigkeiten mit ultraschallschwingungen.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2921467A (en) * 1957-08-21 1960-01-19 Albert L Hedrich Flowmeter compensation for propagation velocity changes
EP0007782A1 (fr) * 1978-07-22 1980-02-06 Robert James Redding Dispositif de mesure de l'écoulement d'un fluide

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENTS ABSTRACTS OF JAPAN, vol. 8, no. 65 (P-263)[1502], 27th March 1984; & JP-A-58 211 667 (TOKYO KEIKI K.K.) 09-12-1983 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5714321A (en) * 1986-11-24 1998-02-03 Gen-Probe Incorporated Nucleic acid probes and methods for detecting salmonella
WO1992017753A1 (fr) * 1991-03-26 1992-10-15 Endress + Hauser Limited Debitmetre acoustique
GB2267568A (en) * 1991-03-26 1993-12-08 Endress & Hauser Ltd Acoustic flowmeter
GB2267568B (en) * 1991-03-26 1994-08-03 Endress & Hauser Ltd Acoustic flowmeter
WO2018095562A1 (fr) * 2016-11-24 2018-05-31 Diehl Metering Gmbh Procédé de mesure de temps du propagation d'un signal ultrasonore dans un fluide en écoulement

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